Typically, a ballast provides power to a lamp and regulates the current and/or power provided to the lamp. Lamps, such as fluorescent lamps, use a ballast to provide the proper starting voltage for the lamp and to control the operating current once the lamp is ignited. One type of fluorescent lamp that is commonly used is a T8 lamp.
Generally, a ballast is configured to provide appropriate and substantially consistent current to the lamp(s) connected thereto. Ballasts sometimes have the capability to detect current feedback from the lamp(s) and adjust the current signal going into the lamp(s) accordingly to ensure substantially consistent operation. This can be done by adjusting the frequency at which an inverter circuit in the ballast drives the lamp(s). However, in certain situations, adjusting the frequency of the inverter circuit can result in damage to the ballast. When a lamp is first connected to a ballast, most ballasts will automatically activate the inverter circuit to begin driving the lamp. There is a period of time upon connection during which the lamp has not reached a normal operating state and the lamp current will be zero or very low. During this time period, if the ballast adjusts the frequency at which the inverter circuit is driving the lamp, it can result in the inverter circuit going into hard switching mode (e.g., a stressful state in which transistors switch rapidly while exposed to full voltage and full current simultaneously), which, in turn, can damage the inverter circuit. It is desirable for the ballast to maintain a relatively constant inverter circuit frequency until the newly connected lamp reaches a normal operating state, and then to adjust the frequency of the inverter circuit to maintain substantially consistent operation of the lamp.